The present invention relates to an improved optical connector sleeve which is used for detachably connecting optical fibers.
With the recent progress of research and development on optical fibers, optical communication systems are finding increasing use. Often optical fibers must be connected. When connecting optical fibers, it is necessary to ensure that transmission loss at joints be reduced as far as possible. When a detachable optical connector is used, it is particularly important to connect the optical fibers without misalignment therebetween. For this purpose, it has been customary to employ a connector sleeve formed precisely from stainless steel or other metals. This sleeve is in the form of a cylinder having an inside diameter which is substantially equal to the outside diameter of a plug having an optical fiber attached thereto so that the plug may be precisely fitted into the sleeve. Since the sleeve is made of a metal, however, it gradually wears as it is repeatedly used for detachable connection. Moreover, a gap may be formed between the sleeve and the plug due to thermal expansion causing misalignment between the optical fibers.
These problems bring about an increase in transmission loss in the sleeve. It has therefore been proposed to use instead of a metal sleeve a sleeve made of ceramic material which has a higher wear resistance and is less subject to thermal expansion than a metal sleeve. The use of ceramic material also has the advantage of facilitating the manufacture of a sleeve with a high degree of dimensional accuracy.
Such a ceramic sleeve, however, still involves a problem. Referring to FIG. 1 of the drawings, there is shown a known ceramic sleeve 3 in which a plug 4 having an optical fiber 1 attached thereto is mounted. If another plug 2 carrying another optical fiber 1 is inserted into the sleeve 3, as shown in FIG. 1, for connecting the two optical fibers 1, the two plugs 2 and 4 fit into the sleeve 3 so tightly that the air in the interior 3a of the sleeve 3 has no place to escape. The air which is compressed between the plugs prevents smooth connection in the sleeve 3. Moreover, any dust trapped in the sleeve 3 or adhering to the plug 2 is also confined inside the sleeve 3 thus further inhibiting smooth connection. Any dust prevent on the end of a fiber can also bring about an increase in transmission loss in the sleeve.
Under there circumstances, it is an object of this invention to provide an improved precisely formed ceramic optical connector sleeve which can connect optical fibers in such a way that there is essentially no transmission loss therebetween, and to provide a ceramic sleeve which permits easy connection of optical fibers.